As shown in FIG. 3, for example, a conventional inspection apparatus includes a main body 1; a mounting table 2 disposed in the main body 1 so as to be movable along X, Y, Z and θ directions while mounting thereon a target substrate (for example, a wafer W); a probe card 3 having a plurality of probes 3A to be brought into contact with a plurality of electrode pads formed on the wafer W loaded on the mounting table 2; a clamp mechanism 4 for fixing the probe card 3 through a card holder (not shown); and a connection ring 5 connecting the probe card 3 and a test head T electrically. The inspection apparatus performs an electrical inspection of the wafer W by receiving and transmitting test signals between a tester (not shown) and the electrode pads on the wafer W via the test head T, the connection ring 5 and the probe card 3. Further, in FIG. 3, a reference numeral 6 denotes an alignment mechanism for performing an alignment of the wafer W and the probe card 3 in cooperation with the mounting table 2, and reference numerals 6A and 6B represent an upper and a lower camera, respectively. Further, a reference numeral 7 denotes a head plate on which the clamp mechanism 4 is fixed.
To inspect the wafer W, an alignment of the wafer W and the probe card 3 is carried out by measuring positions of needles of the probes 3A by the lower camera 6B and measuring the electrode pads on the wafer W corresponding to the probes 3A by the upper camera 6A. After the alignment is completed, the inspection of the wafer W is then carried out. During the inspection, the wafer W and the probe card 3 are brought into contact with each other, and by overdriving the mounting table 2, the wafer W is allowed to be in electrical contact with the probes 3A, so that the inspection of the wafer W is carried out.
However, if the mounting table 2 is overdriven, a heavy contact load is imposed between the mounting table 2 and the probes 3A. If the contact load is excessively heavy, the wafer W would be damaged, whereas, if the contact load is insufficient, inspection reliability may not be achieved due to a contact failure or the like. In this regard, various techniques have been proposed to improve the inspection reliability by allowing the wafer W to make a contact with the probes 3A by a proper overdriving amount. Such techniques are described in Patent References 1 to 3, for example.
In the technique described in Patent Reference 1, there is disposed an optical length-measuring unit for measuring a vertical displacement of a probe card. In this technique, a lifting amount of a mounting table is controlled based on the displacement of the probe card obtained by the optical length-measuring unit, to thereby solve a problem of contact failure between the wafer and the probe card. Further, in the technique disclosed in Patent Reference 2, an overdriving amount of the mounting table can be appropriately set by measuring an absolute displacement of the probe card which is deformed when the mounting table is overdriven. Moreover, in the technique described in Patent Reference 3, the overdriving amount of the mounting table is controlled based on a relation between a sinking amount of the mounting table and a contact load during the overdriving. All of these techniques attempt to obtain an originally intended overdriving amount accurately by considering an influence of sinking of the mounting table and a deformation of the probe card during the overdriving.
(Patent Reference 1)
Japanese Patent Laid-open Application No. 2004-265895
(Patent Reference 2)
Japanese Patent Laid-open Application No. 2003-050271
(Patent Reference 3)
Japanese Patent Laid-open Application No. 2003-168707
However, some probe cards are of a type which makes a contact with a number of electrode pads formed on an entire surface of a wafer W simultaneously. In case of using such a probe card, inspection of electrical characteristic of the wafer W is carried out by allowing the probe card 3 to come into contact with the entire surface of the wafer W on the mounting table 2 simultaneously, as illustrated in FIG. 4. Since the wafer W and the probe card 3 make a contact with each other simultaneously, a contact load increases heavier than in the event that the probe card 3 makes contact with only a part of the wafer W. Besides, if the wafer W has a size of about 300 mm, the number of chips formed thereon increases remarkably along with the high integration of a semiconductor device. Therefore, the number of probes also increases greatly, so that a contact load due to the simultaneous contact between the probe card 3 and the wafer W also increases considerably.
As for a wafer W having a size of, for example, 300 mm, if the contact load due to the simultaneous contact between the probe card 3 and the wafer W increases over, for example, 60 kgf, the contact load exceeds the sum of a reaction force (indicated by an arrow C in FIG. 4) against a spring force of connection terminals (not shown) such as ring-shaped pogo pins arranged in a connection ring 5 as well as the weight of interface mechanism including the weight of the probe card 3 (indicated by an arrow A in FIG. 4) and the weight of the connection ring 5 (indicated by an arrow B in FIG. 4). Accordingly, if the mounting table 2 is lifted as indicated by an arrow D in FIG. 4 to overdrive it, the interface mechanism is lifted even after the occurrence of deformation of the probe card 3 and sinking of the mounting table 2.
Thus, even if the mounting table 2 is overdriven as intended originally, originally intended overdriving amount cannot be obtained and it is difficult to ascertain an accurate lifting amount of the mounting table 2 for achieving the required overdriving amount. Since the techniques of Patent References 1 to 3 do not consider the lifting of the interface mechanism, they cannot ascertain the lifting amount of the mounting table accurately.